Warner-Chappell have a London office (not sure where as they moved) and they should be able to advise where to write. I believe this piano reduction was published circa 1995 but in the US only & included a number of other Korngold pieces from his film music.

If they are unhelpful, post aagain & I'll have another think.
If you are successful, then please post details of your success!

Well I rang up Warner-Chappel's Repetoire dept. and they said they had the full orchestral score for hire (which is cool) but for the piano version I had to ring up the Chappel music store on bond street, which I'm not gonna do just yet as other things have come up, but yeah anyone looking for this score might want to try there.